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| United States Patent |
5,228,917
|
|
Pawlakowitsch
, et al.
|
July 20, 1993
|
Apparatus to reduce the sagging of the outside walls of vacuum tanks
Abstract
Apparatus for reducing the sagging of essentially planar outside walls (3,
13) on a vacuum tank (1) under operating conditions, and for preventing
displacements, resulting therefrom, of components fastened to these
outside walls (3, 13), such as rollers (7, 8) of a winding apparatus (2)
which is movable with respect to the vacuum tank (1) in a vacuum tape
coating apparatus, wherein spacers (12, 14) are provided between two
opposite outside walls (3, 13).
| Inventors:
|
Pawlakowitsch; Anton (Mombris, DE);
Schonherr; Bernhard (Offenbach am Main, DE)
|
| Assignee:
|
Leybold Aktiengesellschaft (Hanau I, DE)
|
| Appl. No.:
|
798631 |
| Filed:
|
November 26, 1991 |
Foreign Application Priority Data
| Current U.S. Class: |
118/50; 118/733 |
| Intern'l Class: |
C23C 014/00 |
| Field of Search: |
118/50,733
427/81,294
|
References Cited
U.S. Patent Documents
| 2989026 | Jun., 1961 | Gardner et al. | 118/733.
|
| 3560166 | Feb., 1971 | Walles | 118/733.
|
| 5085887 | Feb., 1992 | Adams | 118/733.
|
Primary Examiner: Powell; William A.
Attorney, Agent or Firm: Felfe & Lynch
Claims
What is claimed is:
1. Vacuum tape coating apparatus comprising:
a vacuum tank having essentially planar outside walls which tend to sag
under operating conditions and with consequent displacements of components
fastened on these outside walls, comprising:
apparatus that is movable with respect to the vacuum tank, and at least one
spacer between two opposite outside walls.
2. Apparatus according to claim 1, in which the spacer is a spacer rod.
3. Apparatus according to claim 1, in which said fastened components
comprise rollers and in which the movable apparatus has a back plate which
is disposed parallel to the two outside walls and between the latter, and
against which the rollers thrust.
4. Apparatus according to claim 3, in which a spacer rod is disposed
between the outside wall and the opposite back plate of the movable
apparatus.
5. Apparatus according to claim 4, in which the spacer rod is affixed to
the outside wall and to the back plate.
6. Apparatus according to claim 5, which includes a compression rod
disposed in axial prolongation of the spacer rod between back plate and
outside wall.
7. Apparatus according to claim 6, in which the compression rod is affixed
to the outside wall.
8. Apparatus according to claim 3, in which the spacer rod is provided in
the center of a surface of the walls.
9. Apparatus according to claim 3, in which a back plate is provided with
at least one bore.
10. Apparatus according to claim 9, in which at last one spacer rod is
provided with a longitudinally displaceable pressure rod.
11. Apparatus according to claim 9, in which the spacer rod is brought
through the bore of the plate.
12. Apparatus according to claim 10, in which the rod and the piston are
supportable against the outside walls.
Description
BACKGROUND OF THE INVENTION
The invention relates to an apparatus to reduce the sagging of essentially
planar outside walls of vacuum tanks, especially on vacuum tape coating
installations, and to prevent the resultant displacement of components
fastened to these outside walls, such as the rollers of a winding system.
In vacuum tanks there is generally a danger of the deformation and
especially of the sagging in of the tank walls due to the great difference
in the pressure on the two sides of the outside walls. This is true of all
tanks of all sizes and geometric shapes. In a great number of vacuum
tanks, deformation of the kind described above is of minor importance and
can be tolerated.
However, there are applications, such as the vacuum coating of tapes, in
which the sagging in of the tanks is undesirable or unacceptable. Tape
coating apparatus include, as a rule, a stationary vacuum tank with a
movable outer wall--the so-called receptacle plate. On this plate there is
fastened a winding system for carrying the tape that is to be coated. This
winding system includes a plurality of rollers disposed parallel to one
another and journaled between the tank plate and a back plate. On account
of the extremely slight thickness of the tape or film to be coated and the
high speed with which the film runs in the apparatus, the requirements as
to the parallelism of the rollers are very great. Even a slight
misalignment renders the film unusable.
During the coating operation, i.e., when a vacuum prevails in the tank, the
atmospheric pressure against the outer side of the receptacle plate causes
the tank plate to sag inward. Since the back plate is largely free of
external forces, the rollers get out of parallel to a degree depending on
their shape and on how they are mounted.
These undesirable departures from the parallelism of the rollers can be
countered by a more complex construction of the rollers. For example, the
axles of the rollers are made to run all the way through, which creates
the possibility of providing a loose bearing seat at the receptacle plate
end to isolate it largely from the movement of the wall. A disadvantage in
this case is the greater use of material as well as the low natural
frequency of flexural vibrations of the long axle.
Another possibility for reducing o preventing the receptacle plate from
sagging is to provide flexurally stiff structural members on the outside
of the plate as reinforcement. This, however, has considerable
disadvantages as regards production, so that the manufacture of such
receptacle plates is more complex and thus more expensive than that of
plain plates.
The present invention, then, is addressed to the problem of creating an
apparatus which will reduce the sagging in of essentially planar outside
walls on vacuum tanks, prevent resultant displacements of rollers, and
will be simpler and less expensive to make than apparatus known
heretofore.
This problem is solved according to the invention by placing, for example,
a spacer rod between the outer walls of the vacuum chamber, if possible in
the center of the receptacle plate. It will be set at a minimal distance
from the back wall.
Upon the evacuation of the vacuum tank, the forces on the back wall and the
receptacle plate will counteract one another through this prop and thus
advantageously reduce the sagging.
In a mathematical model, the result was a reduction of the maximum sag from
4 mm, for example, to 0.4 mm, which advantageously results in a 90%
reduction of the sagging of the receptacle plate.
Problems with the sagging of outer walls of vacuum tanks of all kinds can
basically be reduced in this manner.
SUMMARY OF THE INVENTION
In accordance with the invention, vacuum tape coating apparatus comprises a
vacuum tank having essentially planar outside walls which tend to sag
under operating conditions and with consequent displacements of components
fastened on these outside walls comprising apparatus that is movable with
respect to the vacuum tank, and at least one spacer between two opposite
outside walls.
For a better understanding of the invention, together with other and
further objects thereof, reference is made to the following description,
taken in connection with the accompanying drawings, and its scope will be
pointed out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention admits of various possibilities of embodiment; two of them
are depicted by way of example in the appended drawings, wherein:
FIG. 1 is a sectional view of a winding system for vacuum tape coating
apparatus according to the state of the art,
FIG. 2 is a sectional view of a winding system according to FIG. 1 under
working conditions,
FIG. 3 is a sectional view of a winding system with a prop according to the
invention, and
FIG. 4 is a sectional view of a winding system with a spacer adjustable
lengthwise.
DESCRIPTION OF PREFERRED EMBODIMENTS
The broken lines in FIG. 1 identify a stationary vacuum tank 1, the solid
lines identify the movable part of a winding system 2. The latter includes
in detail a receptacle plate 3, which closes the vacuum tank 1, and a back
plate 4 disposed parallel thereto. The plates 3 and 4 are joined to one
another by means of the two spacer rods 5 and 6, rods 5 and 6 being at the
greatest possible distance from one another radially. Between plates 3 and
4 the rollers 7 and 8 are oriented parallel to the rods 5 and 6. They are
each made essentially of three parts, namely two short journal stubs 9,
9', 10, 10', which are joined directly to the plates 3 and 4 and to the
actual roller bodies 11 and 11', which are disposed each between a pair of
journal stubs 9, 9', 10, 10'. The tank 1 and the winding system 2 are
disposed in symmetry with the axis A--A.
Under working conditions (FIG. 2) the tank 1 is evacuated and atmospheric
pressure P presses against the outside of the tank 1 and of the receptacle
plate 3. The result is that the receptacle plate 3 sags concavely toward
the interior of the tank 1. Since the back plate 4 is largely free of
external forces, displacements of the components fastened to plate 3 are
the result, i.e., the rollers 7 and 8 flex, spoiling the parallelism of
the rollers 7 and 8 to each other.
FIG. 3 is generally similar to FIG. 1, but in accordance with the invention
it is supplemented by a spacer rod 12 which is disposed between the
receptacle plate 3 and the back plate 4 in the center of the receptacle
plate 3 and parallel to the rods 5 and 6. In axial prolongation of the
spacer rod 12, a compression rod 14 is provided between the back plate 4
and the back wall 13 of the vacuum tank 1, being affixed to the said back
wall 13. It is set at a minimal distance from the back of the back plate
4, so that, when the tank 1 is evacuated, the forces applied by
atmospheric pressure P to the receptacle plate 3 and to the back wall 13
counteract one another and thus reduce the sagging.
In FIG. 4 is shown an embodiment alternative to FIG. 3. Instead of a spacer
rod and compression rod thrusting against a back plate, a back plate 15 is
provided with a bore 16 through which a spacer rod 17 is passed. This rod
17 is provided on one end with a longitudinally displaceable compression
piston 18, so that the rod 17 and the piston 18 are in direct contact with
one another between the two outside walls 3 and 13.
While there have been described what are at present considered to be the
preferred embodiments of this invention, it will be obvious to those
skilled in the art that various changes and modifications may be made
therein without departing from the invention, and it is, therefore, aimed
to cover all such changes and modifications as fall within the true spirit
and scope of the invention.
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